Wheeled carriages for supporting a patient in a substantially horizontal position are well-known in the art and a representative example of an early version of such a device is illustrated in Dr. Homer H. Stryker's U.S. Pat. No. 3,304,116, reference to which is incorporated herein. Dr. Stryker's innovative wheeled carriage included a fifth wheel which is raisable and lowerable by an attendant directly manually manipulating the wheel support frame oriented beneath the patient supporting portion of the wheeled carriage. The fifth wheel is positioned at substantially the center of the undercarriage such that ;usually the rear castered wheels and the fifth wheel support the carriage when the fifth wheel is deployed. However, the front castered wheels and the fifth wheel may also support a patient on the wheeled carriage depending on the position of the patient. Therefore, the wheeled carriage of U.S. Pat. No. 3,304,116 can teeter between the front and rear castered wheels when a patient is being moved thereon with the fifth wheel deployed.
U.S. Pat. No. 3,304,116 to Stryker also shows a top plate for receiving a downward force and positioning the fifth wheel in engagement with a floor surface. Such top plate is located at the top of the undercarriage location which is difficult for an attendant to reach.
A side rail assembly including side rail posts supporting side rails are well known in the art. One such side rail assembly is set forth in U.S. Pat. No. 5,187,824 to Martin Stryker. FIG. 1 thereof illustrates a top rail in a deployed position and FIG. 2 shows the top rail in a collapsed position.
In many side rail assemblies for beds, the side rail posts are made from tubular metal having diameter tolerance variations as well as a plating or a coating surface finish applied thereto. The plating or coating surface finish can extend about an outer circumference thereof. Such a finish improves the feeling and appearance of metal side rail posts. However, such finishes generally have an uneven thickness thus providing a wider range of diameters for the side rail posts. Such a finish interferes with proper seating of the side rail posts because of variations in the radius about a circumference thereof and thus changes tolerances for the posts. Therefore, the tolerances required for support structure supporting the side rail posts must be increased.
However, in general, when the support structure has increased tolerances, pushing or pulling of the deployed side rail, when patients attempt to raise themselves or when support personnel desire to move the bed, causes sway or lateral movement of the rail. Thus, because of the variations in size at the circumference of the side rail posts at their lower end, play exists between a support bracket and a conventional side rail post bolted to the bracket. Thus the side rail can sway in a direction perpendicular to the length of the side rail. Therefore, an arrangement having the side rail posts positively secured to a bracket to prevent swaying is needed.
Accordingly, it is an object of this invention to provide a wheeled carriage for supporting a patient in a substantially horizontal position having at least one auxiliary wheel spaced from the center of gravity of the wheeled carriage such that one set of the castered wheels and the deployed auxiliary wheel, in combination, support the patient during every use of the wheeled carriage generally regardless of the position of the patient.
It is a further object of this invention to provide a cam apparatus having a cam and a cam follower adjacent and below the wheeled base of the wheeled carriage for facilitating a movement of the auxiliary wheel to a position contacting the floor surface. The cam apparatus includes linkages, one linkage having a position control member. The position control member prevents the linkages of the cam apparatus from contacting the floor surface. This arrangement enables the cam apparatus to be a compact part of the wheeled base, thus allowing the wheeled carriage to move the patient support to a lowered position, as needed, to receive a patient from the floor or other location.
It is a further object of the invention to provide an alternate mechanism for raising and lowering the foot end casters to accommodate engagement of the auxiliary wheel with the floor surface.
An object of the invention is to provide a side rail assembly including a support structure for securely mounting the lower end of side rail posts to the frame of a wheeled carriage. Such an arrangement preferably includes having the side rail posts rotatable about their own axes.